Are EM waves additive like sound waves? Or do they remain distinct?

Factual Questions
21

Some beams of light of colour A and B mix and the result is new colour C. When we say colour, it means a spectrum that we perceive as that colour.

Some beams of light of spectrum A and spectrum B mix and the result is new spectrum C

Specturm C is spectrum A added to spectrum B, for each precise frequency range. The waves , or photons, do not join and change frequency to make the new colour C, they remain as they were in the original spectrum.

This allows spectrum analysis of stars.. Helium was first proposed as existing because its absorbtion lines were seen in the spectrum of the sun, the helium gas absobrbing that frequency, hence the name, the gas found in Helios - the sun. Other lines are brighter lines, the emmission from the hot gas. If the frequency changed to follow the percieved colour, by whatever mechansim, the lines seen as emission and absorbtion lines would be erased, the spectrum would just morph to be the new light at the frequency dictated by the resulting spectrum (ie, if its averaging to yellow in an optical sense of averaging, whatever that is, then all the waves becomes yellow waves ?) No.

Spectrums are preserved.

The photons cannot collide and neutralise each other. When the electrons jump energy levels, and have excess energy, they release a photon with that energy , by E=hf , right, There’s an energy conservation with these photons. Photons that would cancel if they were sound or water waves, well no, they, just pass through each other, conserving energy.

22

Sometimes they can. Electronically phased antennas use destructive (and constructive) interference of photons to control where the energy is going.

23

And not even that simple, most sounds we can hear are converted to pitch by where along the length of the cochlea gets stimulated, with lower frequencies stimulating hair cells “deeper” along the cochlea and high frequencies stimulating the start. But very low frequencies can’t do this along any particular point, but instead convert the rate of vibration (mechanical movement) to pitch.